1. Technical Field
The invention includes embodiments that may relate to a single crystal and quasi-single crystal. The invention includes embodiments that may relate to a composition for forming single crystal and quasi-single crystal. The invention includes embodiments that may relate to an apparatus for forming single crystal and quasi-single crystal. The invention includes embodiments that may relate to a method for forming single crystal and quasi-single crystal.
2. Discussion of Related Art
Quasi-single crystal nitrides may be grown by vapor-phase methods, which may employ non-nitride substrates as seeds or substrates to produce quasi-single crystals. Vapor-phase methods may include hydride or halide vapor phase epitaxy, HVPE, and sublimation growth. Control of spontaneous nucleation may be problematic using a non-epitaxial substrate, which may prevent the growth of desirable single crystals. Crystal growth may occur in supercritical fluid. However, the growth rate achievable using conventional autoclaves at mild conditions (temperature less than about 550 degrees Celsius, and pressure less than about 6 kbar) may be undesirably low, and the use of more extreme conditions may require specialized equipment.
Some methods have been disclosed for nitride growth from a flux. A flux is a solvent that is a solid at room temperature. A flux for gallium nitride growth may be molten gallium. However, the vapor pressure of nitrogen gas in contact with the molten gallium may be undesirably high at temperatures sufficiently high for viable crystal growth rates. Such conditions, again, may necessitate the use of specialized equipment. In addition, the growth rates may be undesirably low due to the low solubility and the low diffusion coefficient of nitrogen in molten gallium metal. Small growth rates of gallium nitride in liquid Na/Ga alloys have also been achieved at moderate pressures (about 50 bar). The solubility of nitrogen in liquid Na/Ga alloys is relatively low. The relatively low solubility may limit crystal grow rate and/or maximum crystal size.
Static configurations used for crystal growth, where there is no motion between the hot zone and the growing crystal, may limit crystal grow rate and/or maximum crystal size. A dynamic configuration may include a crystal pulling apparatus, such as a Bridgman apparatus or an apparatus set up for the Czochralski technique. However, the solubility of nitrogen in the flux is relatively low. The dynamic process may be difficult to control because the flux may become supersaturated with respect to gallium nitride formation, and because of spontaneous nucleation of gallium nitride crystals remote from the seed crystal.
It may be desirable to grow Group III metal nitride crystals that are sufficiently large to serve as commercially viable substrates for electronic devices. It may be desirable to grow Group III metal nitride crystals that are of high quality and have low concentrations of impurities and dislocations. It may be desirable to grow Group III metal nitride crystals at a high growth rate.